1. Field of the Invention
This invention relates to a process for purifying industrial waste water. "Industrial waste water" is used herein to mean those waste waters which are primarily of non-domestic origin. Of course the presence of some domestic waste water, as would be present in a large regional treatment facility, is expected, but does not change the essential nature of the waste water from primarily non-domestic. More specifically the invention is directed to a biological process for treating industrial waste water containing impurities which poison or inhibit bacterial forms employed in biological treatment of waste water.
2. Background of the Invention
The growing problem of water pollution has received wide recognition with the increased public interest. Moreover waste water from industrial operations is often given minimal treatment consisting of neutralization of excessive acidity or alkalinity and settling of solids before the treated water is passed into a river, lake or ocean. The treatment corresponds roughly to the familiar primary treatment of municipal sewage. Occasionally, further treatment of the water is carried out through the action of aerobic bacteria on the waste pollutants. This further treatment, known as "secondary" treatment involves the biological decomposition of the waste pollutants by supplying oxygen to bacteria which feed on the combination of oxygen and nutriments in the waste, thereby breaking down much of the waste material into removable solids and carbon dioxide. This "secondary" treatment is commonly practiced by the means of the trickling filter process, oxidation ponds or the activated sludge process. However with those waste waters containing impurities poisonous to bacterial forms employed in these secondary treatments the biological decomposition is inhibited. A "tertiary" treatment, usually treatment with chemicals, is sometimes carried out and is directed to the removal of specific objectionable materials, e.g., ion exchange resins may be used to reduce inorganic content or activated carbon may be used to remove color.
The quantity of pollutants in waste water is commonly determined by measuring the amount of dissolved oxygen required to biologically decompose the waste organic matter in the polluted water. This measurement, called BOD (biochemical oxygen demand), provides an index of the organic pollution of water. Some organic contaminants, such as chlorinated aromatics, are not amenable to conventional biological decomposition and tests such as chemical oxygen demand (COD) and total organic carbon (TOC) have been employed.
Because of the increases in population and industrialization, it is desirable to reduce the time of total waste water treatment and to increase the capacity of treatment plant facilities. Further, since biological degradation is sometimes not satisfactory with industrial wastes which contain the poisonous or inhibiting impurities referred to above, e.g. waste from chemical plants, it is highly desirable to provide a waste treatment process which will accomplish "secondary treatment" and produce a purified effluent comparable to that provided by secondary treatment of municipal waste water.
A process has now been discovered which accomplishes these ends. This process efficiently reduces the biochemical oxygen demand, chemical oxygen demand, and total organic content of the waste water in an unusually rapid manner. In addition the process of this invention greatly increases the rapidity and completeness of sludge settling after treatment of the waste water in an activated sludge process and effectively removes many organic impurities no normally bio-degradable. This process can be employed with industrial waste water alone or with mixtures of industrial waste water and sewage or other waste water.